Hello,

My favorite motorcycle, my RT3, is fouling plugs. I just finished the crankcase seals, base gasket, head gasket, and case cover seals. The oil pump is working and it doesn't smoke too much. Just a puff when you rev it up a bit. I am in Denver at 5000'. I don't know what size main jet I am running. There is no mark on the jet. It is the old style with the o ring. The pilot jet is 45. The needle is set in the middle. It idles good but seems to stutter just a bit mid throttle. It seems like the needle needs to be set leaner. I would like to put in a leaner main jet too. But I could not find a jet to match the main jet. Jets R Us doesn't stock them either. I tried leaning the pilot jet out to a 42.5 but it runs better with the 45.

The first picture is the original jet on top and some jets I got from partzilla that were wrong.
The second and third pics show a new plug after a 4 mile ride.
The fourth and fifth pics show a plug that fouled and left me stranded. LOL.

Does the fouled plug look like the oil pump is putting out too much oil?
Does anyone have access to main jets that are 1 or 2 steps leaner than the stock #230?

Thanks for the help,

Bill

This supplier has them:

lytleracinggroup.com/motorcycle/fuel-int...40-4-pack-4-042-240/

lytleracinggroup.com/other/mikuni-genuin...50-4-pack-4-042-250/

lytleracinggroup.com/other/mikuni-genuin...60-4-pack-4-042-260/

I have 3 RT3s. 2 are regular riders. One of them had a spot seizure at 45 mph. Locked up the back wheel. I ride with 2 fingers on the clutch lever as a habit. Was able to coast to a stop safely. After it cooled down it started up OK and I rode it home. It had a # 230 main jet and a 6DH3 needle with the clip in the middle position. I went up to a # 260 main jet. It still runs good. In my other rider I went up to a # 240 main jet as a precaution. This makes them run a little rich but I don't mind changing spark plugs. The 360 in my opinion needs a little extra fuel than the 250. Gasoline acts as a coolant and lubricant along with oil.

I just realized after looking at your first picture that my previous reply may be not relevant to your situation. All my DT and RT Enduros have the jets without the o-ring on them. Can you post a picture of what your jet screws into?

Also many including me have had some bad results using non Mikuni parts.

The main jet screws into what looks like the float bowl drain plug in the side of the float bowl. Those jets shown will work there.

The top "jet" is not a jet... it's called the "jet setter" in the Yamaha parts book and it's purpose is to use the o-ring to seal the well in the float bowl to the needle jet/emulsion tube.

More pictures of your carb parts with bowl off and "drain plug" out will be helpful.

Thanks for the information guys. I will look for the main jet in the drain looking thing in the bowl. I seem to remember that I changed a main jet on my old rt3 15 years ago and I had forgotten since. LOL.

Those main jets are right. Follow Marks advice & are in the bowl drain looking bung, Oring is critical but yours looks good for sealing into the bowl. Thing is, what changed between the plugs that look quite good & the oily wet ones. Choked up exhaust or aircleaner. RH crank seal--doubt it though. Will it rev out in neutral or just flood up. Be sure the flywheel is super tight & crank key is of as they love to devour them.

Hey Guys,

Good news. I put in the new jet and the bike is happy. I had two other 360s and this one is running better than either of them.

I have had the bike about two years and the plug was always rich and would foul plugs sometimes. New crank seals and gaskets put it over the edge. The altitude is a big factor. I have made out flipping bikes that aren't adjusted for it.

On to the next thing. The bike is completely sorted, but.... The front wheel pulses when I hit the brakes. I have been searching around Denver for someone to turn the front wheel brake drum and have not had any luck. It might be a dying art. Does anyone know someone who can turn a front wheel?

Thanks again for the help,

Bill

Yes re--the front brake drum, i've only ever come across one like that & that was a trick magnesium suzy RM front wheel but couldn't find anyone to swing the whole thing so un-built it & it spun almost perfect so built it up again & it pulled the drum out of shape--so gave up for now. One thing out of the ordinary though that can cause it --& highly unlikely--is if the bearing housing has flogged out & the loose bearing is sitting to one side it'll make the hub gyrate around the axle rather than be true to center. Never had that in a 250/360 wheel though.

RaceTech in California did at one time I think... never has been common for bikes that I remember.

You might try loosening the axle, pull the brake, and then tighten the axle... I remember reading something about doing that to center things... doesn't make much sense but it's cheap and easy to try.